Static random access memory (SRAM) is a type of semiconductor memory. The word “static” indicates that the memory retains its contents as long as power remains applied, unlike dynamic RAM (DRAM) that needs to be periodically refreshed with its memory content. However, SRAM should not be confused with read-only memory or flash memory. SRAM is volatile memory, preserving data only while power is continuously applied.
There are different types of SRAM cells. One common form of SRAM cell is a six-transistor (6T) SRAM cell. A 6T SRAM cell includes two cross-coupled inverters, where the gates of the transistors of each of the inverters is coupled to the commonly-coupled drains of the transistors of the other inverter. Each of these commonly-coupled drain nodes are coupled to a bitline via a pass transistor.